Ever increasing attention is being paid to detection and analysis of low concentrations of analytes in various biologic and organic environments. Qualitative analysis of such analytes is generally limited to the higher concentration levels, whereas quantitative analysis usually requires labeling with a radioisotope or fluorescent reagent. Such procedures are time consuming and inconvenient. Thus, it would be extremely beneficial to have a quick and simple means of qualitatively and quantitatively detecting analytes at low concentration levels.
Solid-state sensors and particularly biosensors have received considerable attention lately due to their increasing utility in chemical, biological, and pharmaceutical research as well as disease diagnostics. In general, biosensors consist of two components: a highly specific recognition element and a transducing structure that converts the molecular recognition event into a quantifiable signal. Biosensors have been developed to detect a variety of biomolecular complexes including oligonucleotide pairs, antibody-antigen, hormone-receptor, enzyme-substrate and lectin-glycoprotein interactions. Signal transductions are generally accomplished with electrochemical, field-effect transistor, optical absorption, fluorescence or interferometric devices.
It is known that the intensity of the visible reflectivity changes of a porous silicon film can be utilized in a simple biological sensor, as disclosed in U.S. Pat. No. 6,248,539 to Ghadiri et al. As disclosed therein, the detection and measurement of the wavelength shifts in the interference spectra of a porous semiconductor substrate such as a silicon substrate make possible the detection, identification and quantification of small molecules. While such a biological sensor is certainly useful, its sensitivity is lacking in that detection of a reflectivity shift is complicated by a broad peak rather than one or more sharply defined luminescent peaks.
The present invention is directed to overcoming these and other deficiencies in the art.